1. Field of the Invention
The present invention relates to a semiconductor device and a noise measuring method. More particularly, the present invention relates to a semiconductor device for measuring noise generated within the semiconductor device and a noise measuring method.
2. Description of the Related Art
In recent years, a Large Scale Integrated circuit (LSI) malfunctioning by power noise or signal noise generated during its operation is found here and there.
To take measures against this LSI malfunction, an LSI for directly measuring noise within the device and outputting the noise as noise information to the outside is known.
FIG. 12 is a construction view showing a conventional semiconductor device for obtaining and outputting noise information.
Here, a solid arrow indicates a flow of observational data and a dotted arrow indicates a flow of control signals.
A conventional semiconductor device 800 has a sampling oscilloscope 810 for inputting analog noise information from a to-be-observed node 801, a communication section 820 for communicating with the outside of the semiconductor device 800, and a controller 830 for controlling each section of the semiconductor device 800.
The sampling oscilloscope 810 has an Analog Digital Converter (ADC) 811, a delay circuit 812, a counter 813, and a memory 814.
When analog noise information is input from the to-be-observed node 801, the ADC 811 analog-to-digital converts the noise information and records the information in the memory 814. The counter 813 counts a clock signal and records the signal in the memory 814 as time information. The delay circuit 812 has a function of assuming a periodicity of a noise waveform and reducing the number of data to be sampled.
In the conventional semiconductor device 800, when a reading request of noise information is issued from the outside, that effect is inputted to the controller 830 via the communication section 820. The controller 830 reads out as noise information the noise information of digital value and time information recorded in the memory 814 and outputs the noise information to the outside via the communication section 820.
Thus, in the conventional semiconductor device 800, the data amount to be handled can be reduced by assuming that a noise waveform is periodic. As a result, noise information can be obtained by the inexpensive ADC 811.
However, real noise rarely appears periodically. A real semiconductor device generates noise non-periodically due to the data or command to be processed. Therefore, the conventional semiconductor device based on the periodicity of noise is impractical.
Further, the conventional semiconductor device has a problem that when the whole non-periodic noise information is handled, the data amount becomes enormous.